Extension cords have been used for many years to lengthen the cord of an electrical device so that it can be connected to a power supply or receptacle. One end of the extension cord is formed with a socket or receptacle that is sized to engage with a plug located on the cord of the electrical device while the other end of the extension cord is formed with a plug which is adapted to engage with a socket located at the power supply.
Quite often, while the user is moving the electrical device or when the extension cord or cord of the device becomes entangled or otherwise caught, the extension cord will become disconnected from the device or power supply. When this occurs, the user is forced to discontinue operations and to re-establish the electrical connection, thereby adding additional time to complete the task. Yet worse, the extension cord may become partially disconnected from the receptacle, thereby leaving the "hot" electrical contacts exposed to the user and the environment. In this situation, a person may accidently come in contact with the electrical contacts and sustain sever injuries or the electrical contacts may become shorted thereby causing a fire and/or damage to the device, power supply or user.
In order to prevent the extension cord from becoming disconnected from the device, users have often resorted to means such as tying the cord of the device and the socket end of the extension cord into a knot to thereby isolate the plug/socket connection from any induced stress. This method, however, is time consuming, may damage the insulation surrounding the conductor, and shortens the effective length of the cord.
To overcome the above disadvantages, extension cords have been designed with a variety of locking mechanisms to securely connect the extension cord to the device or power supply. One such extension cord is shown in U.S. Pat. No. 4,085,991 (FIGS. 5 and 6) and includes a socket having a pair of legs 56 each of which are rotatably mounted about a pin 58. A finger 60 is mounted at the midpoint of each leg 56 and adapted so that when the leg 56 is rotated inward, the finger 60 becomes engaged with the apertures formed in plug 24. To remove the plug 24, the fingers 60 are compressed at a position above the pivot pin 58 which causes the legs 56 to rotate outwardly of the recess 44 and the fingers 60 to become disengaged from the apertures of the plug 24.
Extension cords of the type exemplified by U.S. Pat. No. 4,085,991, however, have several disadvantages. First, the legs which carry the fingers are completely exposed to the user and are pivoted about a pin. In order to successfully lock and unlock the extension cord, a user must apply pressure to the correct portion of the leg. Secondly, movement of the legs outside of the housing creates a spacing between the legs and the housing and an open passage between the environment and the electrical contacts of the socket. As such, a person's finger or clothes may become caught therein or the electrical contacts may become exposed to water or foreign materials which might create a dangerous working condition.
One object of the invention was to design an extension cord having a locking feature which could be easily actuated by the user.
Another object of the present invention was to design an extension cord that could be safely used in all types of weather conditions and working environments.